Measurement of the tt̅ cross section in pp̅ collisions at √s=1.96 TeV using dilepton events with a lepton plus track selection

This paper reports a measurement of the cross section for the pair production of top quarks in ppbar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron. The data was collected from the CDF II detector in a set of runs with a total integrated luminosity of 1.1 fb^{-1}. The cross section is measured in the dilepton channel, the subset of ttbar events in which both top quarks decay through t -> Wb -> l nu b where l = e, mu, or tau. The lepton pair is reconstructed as one identified electron or muon and one isolated track. The use of an isolated track to identify the second lepton increases the ttbar acceptance, particularly for the case in which one W decays as W -> tau nu. The purity of the sample may be further improved at the cost of a reduction in the number of signal events, by requiring an identified b-jet. We present the results of measurements performed with and without the request of an identified b-jet. The former is the first published CDF result for which a b-jet requirement is added to the dilepton selection. In the CDF data there are 129 pretag lepton + track candidate events, of which 69 are tagged. With the tagging information, the sample is divided into tagged and untagged sub-samples, and a combined cross section is calculated by maximizing a likelihood. The result is sigma_{ttbar} = 9.6 +/- 1.2 (stat.) -0.5 +0.6 (sys.) +/- 0.6 (lum.) pb, assuming a branching ratio of BR(W -> ell nu) = 10.8% and a top mass of m_t = 175 GeV/c^2.

Measurement of the top quark mass at CDF using the “neutrino ϕ weighting” template method on a lepton plus isolated track sample

We present a measurement of the top quark mass with t-tbar dilepton events produced in p-pbar collisions at the Fermilab Tevatron $\sqrt{s}$=1.96 TeV and collected by the CDF II detector. A sample of 328 events with a charged electron or muon and an isolated track, corresponding to an integrated luminosity of 2.9 fb$^{-1}$, are selected as t-tbar candidates. To account for the unconstrained event kinematics, we scan over the phase space of the azimuthal angles ($\phi_{\nu_1},\phi_{\nu_2}$) of neutrinos and reconstruct the top quark mass for each $\phi_{\nu_1},\phi_{\nu_2}$ pair by minimizing a $\chi^2$ function in the t-tbar dilepton hypothesis. We assign $\chi^2$-dependent weights to the solutions in order to build a preferred mass for each event. Preferred mass distributions (templates) are built from simulated t-tbar and background events, and parameterized in order to provide continuous probability density functions. A likelihood fit to the mass distribution in data as a weighted sum of signal and background probability density functions gives a top quark mass of $165.5^{+{3.4}}_{-{3.3}}$(stat.)$\pm 3.1$(syst.) GeV/$c^2$.

Search for New Physics with a Dijet Plus Missing ET Signature in pp̅ Collisions at √s=1.96 TeV

We present results of a signature-based search for new physics using a dijet plus missing transverse energy data sample collected in 2 fb-1 of p-pbar collisions at sqrt(s) = 1.96 TeV with the CDF II detector at the Fermilab Tevatron. We observe no significant event excess with respect to the standard model prediction and extract a 95% C.L. upper limit on the cross section times acceptance for a potential contribution from a non-standard model process. Based on this limit the mass of a first or second generation scalar leptoquark is constrained to be above 187 GeV/c^2.

Measurement of the tt̅ production cross section in 2 fb-1 of pp̅ collisions at √s=1.96 TeV using lepton plus jets events with soft muon b tagging

We present a measurement of the tt̅ production cross section in pp̅ collisions at √s=1.96  TeV using events containing a high transverse momentum electron or muon, three or more jets, and missing transverse energy. Events consistent with tt̅ decay are found by identifying jets containing candidate heavy-flavor semileptonic decays to muons. The measurement uses a CDF run II data sample corresponding to 2  fb-1 of integrated luminosity. Based on 248 candidate events with three or more jets and an expected background of 79.5±5.3 events, we measure a production cross section of 9.1±1.6  pb.

Measurement of the tt̅ production cross section in 2 fb-1 of pp̅ collisions at √s=1.96 TeV using lepton plus jets events with soft muon b tagging

We present a measurement of the tt̅ production cross section in pp̅ collisions at √s=1.96  TeV using events containing a high transverse momentum electron or muon, three or more jets, and missing transverse energy. Events consistent with tt̅ decay are found by identifying jets containing candidate heavy-flavor semileptonic decays to muons. The measurement uses a CDF run II data sample corresponding to 2  fb-1 of integrated luminosity. Based on 248 candidate events with three or more jets and an expected background of 79.5±5.3 events, we measure a production cross section of 9.1±1.6  pb.

Measurement of the tt̅ production cross section in 2 fb-1 of pp̅ collisions at √s=1.96 TeV using lepton plus jets events with soft muon b tagging

We present a measurement of the $\ttbar$ production cross section in $\ppbar$ collisions at $\sqrt{s}=1.96$ TeV using events containing a high transverse momentum electron or muon, three or more jets, and missing transverse energy. Events consistent with $\ttbar$ decay are found by identifying jets containing candidate heavy-flavor semileptonic decays to muons. The measurement uses a CDF Run II data sample corresponding to $2 \mathrm{fb^{-1}}$ of integrated luminosity. Based on 248 candidate events with three or more jets and an expected background of $79.5\pm5.3$ events, we measure a production cross section of $9.1\pm 1.6 \mathrm{pb}$.

Quantum kinematics of Fermi-Dirac vacuum-plus-one-electron problem

Following Weisskopf, the kinematics of quantum mechanics is shown to lead to a modified charge distribution for a test electron embedded in the Fermi-Dirac vacuum with interesting consequences.

Effect of mode of rolling on development of texture and microstructure in two-phase (alpha plus beta) brass

The evolution of microstructure and texture during deformation of two-phase (alpha + beta) brass was studied for different initial microstructure and texture. The deformation processing involved unidirectional and multi-step cross-rolling. The bulk textures were determined by measuring the pole figures and calculating the orientation distribution function ODF for both alpha (fcc) and beta (bcc) phases, while the microstructure and other microstructural parameters were measured through optical microscopy and scanning electron microscopy with electron back scatter diffraction (SEM-EBSD). Results indicate that textures developed after unidirectional rolling and multi-step cross-rolling are significantly different. The variation in initial texture had a pronounced effect on the development of texture in the alpha phase during subsequent deformation. (C) 2010 Elsevier B.V. All rights reserved.

Methyl ethyl ketone plus water plus secondary butyl alcohol: A potential system for the exploration of a quadruple critical point

We report preliminary experiments on the ternary-liquid mixture, methyl ethyl ketone (MEK)+water (W)+secondary butyl alcohol (sBA)-a promising system for the realization of the quadruple critical point (QCP). The unusual tunnel-shaped phase diagram shown by this system is characterized and visualized by us in the form of a prismatic phase diagram. Light-scattering experiments reveal that (MEK+W+sBA) shows near three-dimensional-Ising type of critical behavior near the lower critical solution temperatures, with the susceptibility exponent (gamma) in the range of 1.217 <=gamma <= 1.246. The correlation length amplitudes (xi(o)) and the critical exponent (nu) of the correlation length (xi) are in the ranges of 3.536 <=xi(o)<= 4.611 A and 0.619 <=nu <= 0.633, respectively. An analysis in terms of the effective susceptibility exponent (gamma(eff)) shows that the critical behavior is of the Ising type for MEK concentrations in the ranges of 0.1000 <= X <= 0.1250 and X >= 0.3000. But, for the intermediate range of 0.1750 <= X < 0.3000, the system shows a tendency towards mean-field type of critical behavior. The advantages of the system (MEK+W+sBA) over the system (3-methylpyridine+water+heavy water+potassium Iodide) for the realization of a QCP are outlined.

European aspen and hybrid aspen under changing environment : Leaf traits, growth and litter decomposition

Understanding the responses of species and ecosystems to human-induced global environmental change has become a high research priority. The main aim of this thesis was to investigate how certain environmental factors that relate to global change affect European aspen (Populus tremula), a keystone species in boreal forests, and hybrid aspen (P. tremula × P. tremuloides), cultivated in commercial plantations. The main points under consideration were the acclimatization potential of aspen through changes in leaf morphology, as well as effects on growth, leaf litter chemistry and decomposition. The thesis is based on two experiments, in which young aspen (< 1 year) were exposed either to an atmospheric pollutant [elevated ozone (O3)] or variable resource availability [water, nitrogen (N)]; and two field studies, in which mature trees (> 8 years) were growing in environments exposed to multiple environmental stress factors (roadside and urban environments). The field studies included litter decomposition experiments. The results show that young aspen, especially the native European aspen, was sensitive to O3 in terms of visible leaf injuries. Elevated O3 resulted in reduced biomass allocation to roots and accelerated leaf senescence, suggesting negative effects on growth in the long term. Water and N availability modified the frost hardening of young aspen: High N supply, especially when combined with drought, postponed the development of frost hardiness, which in turn may predispose trees to early autumn frosts. This effect was more pronounced in European aspen. The field studies showed that mature aspen acclimatized to roadside and urban environments by producing more xeromorphic leaves. Leaf morphology was also observed to vary in response to interannual climatic variation, which further indicates the ability of aspen for phenotypic plasticity. Intraspecific variation was found in several of the traits measured, although intraspecific differences in response to the abiotic factors examined were generally small throughout the studies. However, some differences between clones were found in sensitivity to O3 and the roadside environment. Aspen leaf litter decomposition was retarded in the roadside environment, but only initially. By contrast, decomposition was found to be faster in the urban than the rural environment throughout the study. The higher quality of urban litter (higher in N, lower in lignin and phenolics), as well as higher temperature, N deposition and humus pH at the urban site were factors likely to promote decay. The phenotypic plasticity combined with intraspecific variation found in the studies imply that aspen has potential for withstanding environmental changes, although some global change factors, such as rising O3 levels, may adversely affect its performance. The results also suggest that the multiple environmental changes taking place in urban areas which correspond closely with the main drivers of global change can modify ecosystem functioning by promoting litter decomposition, mediated partly by alterations in leaf litter quality.

Role of Water in the Enzymatic Catalysis: Study of ATP plus AMP -> 2ADP Conversion by Adenylate Kinase

The catalytic conversion ATP + AMP -> 2ADP by the enzyme adenylate kinase (ADK) involves the binding of one ATP. molecule to the LID domain and one AMP molecule to the NMP domain. The latter is followed by a. phosphate transfer and then the release of two ADP molecules. We have computed a novel two-dimensional configurational free energy surface (2DCFES), with one reaction coordinate each for the LID and the NMP domain motions, while considering explicit water interactions. Our computed 2DCFES clearly reveals the existence of a stable half-open half-closed (HOHC) intermediate stale of the enzyme. Cycling of the enzyme through the HOHC state reduces the conformational free energy barrier for. the reaction by about 20 kJ/mol. We find that the stability of the HOHC state (missed in all earlier studies with implicit solvent model) is largely because of the increase of specific interactions of the polar amino acid side chains with water, particularly with the arginine and the histidine residues. Free energy surface of the LID domain is rather rugged, which can conveniently slow down LID's conformational motion, thus facilitating a new substrate capture after the product release in the catalytic cycle.

Antimicrobial Properties of Nanostructured TiO2 Plus Fe Additive Thin Films Synthesized by a Cost-Effective Sol-Gel Process

We prepared thin films composed of pure TiO2 or TiO2 with an Fe additive (at concentrations of 0.2-0.8 wt%) via a simple and cost effective sol gel process, and tested their antifungal properties (against Candida albicans (MTCC-1637), Candida tropicalis (MTCC-184), Candida parapsilosis (MTCC-2509), and Candida glabrata (MTCC-3019) and antibacterial properties (against Staphylococcus faecalis (NCIM-2604) Staphylococcus epidermidis (NCIM-2493), Staphylococcus aureus (NCIL-2122), and Bacillus subtilis (NCIM-2549)). The films were deposited on glass and Si substrates and subjected to annealing at 400 degrees C for 3 h in ambient air. The film structural and morphological properties were investigated by X-ray photoelectron spectroscopy profilometry and scanning electron microscopy, respectively. Antifungal and antibacterial tests were conducted using the drop test method. Among the species examined, Candida albicans (MTCC-1637), and Staphylococcus aureus (NCIL-2122) showed complete colony formation inhibition after exposure for 4 h for the TiO2 loaded with 0.8 wt% Fe thin films. These results indicate that increasing the Fe concentration increased the antimicrobial activity, with complete inhibition of colony formation after 4 h exposure.

Surfactant solubility and micellization in ternary eutectic melt (acetamide plus urea plus ammonium nitrate)

Cationic surfactants such as dodecyltrimethylammonium bromide (DTAB), tetradecyltrimehtylammonium bromide (TTAB) and hexadecyltrimethylammonium bromide (HTAB); and anionic surfactants such as sodium decyl sulphate (SDeS), sodium dodecyl sulphate (SDS) and sodium tetradecyl sulphate (STDS) have been used to determine their solubility and micellization in ternary eutectic melt (acetamide + urea + ammonium nitrate) at 50 degrees C. We employed the electrical conductivity and the surface tension measurement techniques to determine the critical micelle concentration (CMC). The deviation in the slope of the specific conductance/surface tension against surfactant concentration plots indicated the aggregations of surfactants and hence, their CMC. CMC decreases with increase of alkyl chain length due to the increased van der Waals forces. The calculated increment in Gibb's energy per methylene group for cationic and anionic surfactants is about -6 kJ mol(-1) and -4 kJ mol(-1) respectively. It is found that, the CMCs of the surfactants in the ternary melt are higher than the CMCs of same surfactants in water (similar to 25 degrees C). (C) 2012 Elsevier B.V. All rights reserved.

Ultrahigh-temperature metamorphism from an unusual corundum plus orthopyroxene intergrowth bearing Al-Mg granulite from the Southern Marginal Zone, Limpopo Complex, South Africa

The Southern Marginal Zone of the Limpopo Complex is composed of granite-greenstone cratonic rocks reworked by a Neoarchean high-grade tectono-metamorphic event. Petrographic and mineral chemical characterization of an Al-Mg granulite from this zone is presented here. The granulite has a gneissic fabric with distinct Al-rich and Si-rich layers, with the former preserving the unusual lamellar (random and regular subparallel) intergrowths of corundum and symplectic intergrowth of spinel with orthopyroxene. The Al-rich layer preserves mineral assemblages such as rutile with orthopyroxene + sillimanite +/- A quartz, Al-rich orthopyroxene (similar to 11 wt%), spinel + quartz, and corundum in possible equilibrium with quartz, while the Si-rich layer preserves antiperthites and orthopyroxene + sillimanite +/- A quartz, all considered diagnostic of ultrahigh-temperature metamorphism. Application of Al-in-opx thermometry, ternary feldspar thermometry and construction of suitable pressure-temperature phase diagrams, compositional and model proportion isopleth results indicate P-T conditions as high as similar to 1,050-1,100 A degrees C, and similar to 10-12 kbars for the Al-Mg granulite. Our report of ultrahigh-temperature conditions is significant considering that the very high temperature was reached during decompression of an otherwise high-pressure granulite complex (clockwise P-T path), whereas most other ultrahigh-temperature granulites are linked to magma underplating at the base of the crust (counterclockwise P-T path).